1. Field of the Invention
The present invention relates to an input device with display function for performing input operation to a digitizer (a coordinate position inputting sensor) based on, for example, an electromagnetic resonance technology.
2. Description of the Related Art
In recent years, there has been proposed an input device with liquid crystal display function to be applied to an electronic device such as a personal computer, a PDA (personal digital assistant) or the like. There also has been proposed a position detecting device in which a shield plate is used (see Japanese Unexamined Patent Application Publication No. 2005-275381 and Japanese Unexamined Patent Application Publication No. 2006-309308).
FIG. 12 shows the internal structure of an input device with liquid crystal display function according to related art. In such an input device, a protective plate 121 made of glass, for example, is bonded to an upper case 127 with an adhesive 131. A silk-screen printed portion 130 for shielding light is provided on a lower surface of an end portion of the protective plate 121.
A liquid crystal cell 122 is arranged in a lower case 128. A liquid crystal back light 123 and a liquid crystal back light unit 124 are fixed to the liquid crystal cell 122 via a metal bezel 126 by screwing screws 129 into bosses 134 in the lower case 128. A flat shaped digitizer 125 is arranged under a rear surface of the liquid crystal back light unit 124.
As seen in FIG. 12, since an air layer 133 exists between the liquid crystal cell 122 attached to the lower case 128 and the protective plate 121 attached to the upper case 127, all assembly of the input device, as seen in FIG. 12, is performed in a clean room so that no dust and the like is mixed into the air layer 133.
FIG. 13 shows the internal structure of an input device with liquid crystal display function according to another related art. In such an input device, a protective plate 141 is bonded to a liquid crystal cell 142 with an adhesive 151. A silk-screen printed portion 150 for shielding light is provided on a lower surface of an end portion of the protective plate 141. An upper case 147 is arranged so as to cover the end portion of the protective plate 141.
A liquid crystal back light 143 and a liquid crystal back light unit 144 are fixed to the liquid crystal cell 142 via a metal bezel 146 by screwing screws 149 into the bosses in a lower case 148. A flat shaped digitizer 145 is arranged under a rear surface of the liquid crystal back light unit 144.
As seen in FIG. 13, an air layer 153 exists between the protective plate 141 and the liquid crystal cell 142. In this case, all assembly of the input device, except for the process of bonding the protective plate 141 to the liquid crystal cell 142 with the adhesive 151, can be performed in a normal environment, instead of being performed in a clean room (see FIG. 13).
In the input devices with liquid crystal display function having the aforesaid arrangements, input operation is performed with, for example, a stylus pen (not shown). Specifically, input operation is performed by abutting the pen-tip of the stylus pen against the protective plates 121 or 141 to draw an illustration or write a character, just like drawing or writing with an ordinary ballpoint pen or pencil. Further, input operation is detected and converted into digital data by the digitizers 125 or 145, and the digital data is inputted into a personal computer, a PDA, or the like, so that a handwriting input operation, such as drawing an illustration or writing a character, can be performed on the computer and the like.